Multidimensional resource partitioning by Serengeti herbivores

The enchanting diversity of large mammalian herbivores in African savannas has long challenged ecologists: How can so many species of large, generalist plant eaters coexist? Variation in body size and craniofacial/dental anatomy are key morphological determinants of ecological niche differentiation, shaping foraging behavior in ways that stabilize coexistence by limiting interspecific competition for space and food. Variation in water requirements may be another important dimension of niche differentiation, but whether and how variability in water requirements affects the partitioning of other resources is unknown. Here, we investigate how body size, dental morphology, and water requirements interactively affect space use and diet of 15 large-herbivore species in Serengeti National Park. Water requirements predicted space use in relation to permanent water sources, while diet type (percentage grass) was best predicted by dental morphology. Food partitioning was best predicted by a combination of all three traits in both wet and dry seasons. Furthermore, the total explained variation of diet dissimilarity explained almost tripled when these three traits were combined compared to single traits, emphasizing the importance of multiple dimensions of niche differentiation. Our results show that variation in water requirements is strongly associated with spatial and dietary niche differentiation among large herbivores, emphasizing the importance of spatial heterogeneity in surface water and vegetation structure for maintaining the world's last mega-diverse megafaunal assemblages. Integrating multiple dimensions of resource partitioning is a crucial step toward predicting how species will respond to homogenization of savanna landscapes due to changes in land use, surface water availability, and rainfall.